In the related art, for example, in a field winding rotary electric machine for vehicle, component members are being highly integrated due to downsizing of a rotary electric machine and upsizing of wiring members to meet the demands for improvement of fuel efficiency and a higher output.
Members forming a rotary electric machine are reduced in size and installed in a crammed fashion to meet the demand that the rotary electric machine be downsized, and clearances among the members are becoming smaller. In particular, wirings are becoming more complicated in a motor generator that includes an inverter portion formed of power semiconductor elements performing switching operations in the interior than in an alternator that uses a rectifier formed of diode elements. Accordingly, a degree of integration of component members in the interior of the rotary electric machine becomes higher.
Further, to meet the demand for a higher output, a current flowing to brushes that supply a field current to the power semiconductor elements and a field winding, a field winding portion provided to a rotor, and an armature winding portion provided to a stator is increasing and so is an amount of heat generated in the respective portions. Herein, there may be a need to upsize the members depending on magnitude of the current.
Also, a brush holder that holds the brush and protects the brush from foreign matter from the outside is attached to the brush. The brush holder is installed in the vicinity of a power circuit portion from its current path. For these reasons, arrangement density of component members is particularly high in the periphery of the power circuit portion and the brush portion.
However, the structure of the rotary electric machine allows foreign matter, such as dust, to readily enter the vicinity of the power portion and the brush holder. Although the rotary electric machine is installed inside the engine room of the vehicle, a member, such as a housing, is provided with a large number of openings for intake of cooling air. Foreign matter, such as dust and a corrosion product produced by salt water, coming inside from these openings enters the interior of the rotary electric machine.
In such cases, foreign matter, such as dust and a corrosion product produced by salt water, deposits in the vicinity of a heat sink connected to a power module and the brush holder and eventually clogs a ventilation path of cooling air or fins of the heat sink or causes a deficiency arising from a short circuit between current-passing members. Consequently, the rotary electric machine suffers a breakdown or an operational failure and cooling performance for the component members is deteriorated.
Also, in the rotary electric machine for vehicle, a field current is supplied from the brush to the field winding of the stator via a slip ring. In this instance, the brush slides while being pressed against the slip ring by a spring attached behind the brush. The brush and the slip ring generate heat caused by an electrical loss in the sliding portion, sliding friction, and electrical losses in their own current-passing paths. A pair of the slip ring and the brush is provided on each of a plus side and a minus side. Hence, in order to ensure electrical insulation between the plus side and the minus side, the brushes and the slip rings are generally covered with insulating resin or the like and retained. In addition, the brush holder storing the brush therein prevents entry of foreign matter and moisture from the outside and is also furnished with a function of discharging brush abrasion powder.
Hence, a slight clearance is provided to discharge brush abrasion powder. However, a percentage of cooling air generated by a cooling fan installed to the rotor and supplied to an abutting portion of the slip ring and the brush is small. Because of these factors, the slip rings and the brushes become hot particularly at the abutting portion.
For example, PTL 1 (JP-A-2006-166681) describes a rotary electric machine for vehicle. This rotary electric machine for vehicle has a power circuit portion formed of switching elements and a pair of inverter modules connected to the switching elements in parallel and a control circuit portion that controls the power circuit portion. With respect to a flow of cooling air generated by a centrifugal fan firmly attached to the rotor, the control circuit portion is installed upstream and the power circuit portion is separately installed downstream. The control circuit portion is provided with a through-hole so that the cooling air flows linearly by way of the power circuit portion.
Also, PTL 2 (JP-A-2004-274992) describes an idling stop control device. This control device includes switching elements directly fixed onto a heat sink of substantially a disc shape and a circuit board having a printed wiring layer fixed onto the heat sink. A control IC and the like are attached onto this circuit board. Double side-frame portions are attached along an entire outer periphery and an entire inner periphery of the heat sink. The heat sink is fixed to a rear-end outer wall of a bracket via the outer peripheral side-frame portion. A ring-like concave portion surrounded by the inner and outer peripheral side-frame portions of the heat sink is filled with resin. Owing to this structure, the switching elements, the circuit board, the control IC, and the like are readily protected from environmental factors, such as brine mud water. Hence, durability and reliability can be enhanced.
Also, the control device has a cooling structure by which a resin cover covering the heat sink is fixed to the bracket, and cooling air flowing in from air inlet holes provided to the resin cover flows into the bracket while cooling the heat sink and is blown off to the outside from the bracket after it cools the stator winding and the rotor winding.